Ferroelectric and piezoelectric composition

ABSTRACT

X Y Z   A 75 0 25 B 60 10 30 C 10 60 30 D 5 55 40 E 5 45 50 F 15 30 55 G 35 10 55 H 35 0 45 IS DISCLOSED. THE CONSTITUENTS ARE DEFINED BY THE FORMULA X+Y+Z=100 WHEREIN X, Y AND Z ARE IN THE FOLLOWING RANGES TAKEN WITH REFERENCE TO THE FIGURE ABCDEFGH IN FIG. 1: FERROLECTRIC AND PIEZOELECTRIC COMPOSITION COMPRISING A SOLID SOLUTION OF THE TERNARY SYSTEM   X(PB(IN1/2NB1/2)O3)-Y (PBZRO3)-Z (PBTIO)

Dec. 28, 1971 MITSUO OSADA EIAL 3,630,908

FERROEL'ECTRIC AND PIEZOELECTRIC COMPOSITION Filed March 1.1, 1968 2 Sheets-Sheet 1 Tri ar Compositional Diagram The Ternary Sysiem Pb(|n Nb )O PbZr O3-PbTiO3(mol%) Pbfln Nb 0 INVENTORS Mifsuo Osada Osarnu Kumon Tafsuya Nlls/uknolo ATTO NEYS iZy z %%%M/ 4.

Dec. 28, 1971 MITSUO OSADA ETAL 3,630,908

FERROELE'CTRIC AND PIEZOELECTRIC COMPOSITION- Filed March 11, 1968 r '2 Sheets-Sheet 2 Variation In The Longitudinal Coupling Coefficient(K )And The Dielectric 2000 Constant (E) Versus Pb(In Nb'/ O -PbTi o Concentration IOOO 50 4O 3O 20-' i mol PDTIO3 I h d [500 Variation lnT e Longitu ma Coupling Coefficient (K And The Dielectric Constant (E)\lersus PbTiO PbZrO 5 Concentration [Pbfln Nb O O Constant At IOmois IOOO X=|Omol -|O 5O 4O 5O-'-PbTi0 6O 5O 4O"PbZrO mol 0 INVENTORS M/fsuo Osada Osamu Kumon 3 Tafsuya M'sh/mafo 1 BY J WWW ATTO NEYS United States Patent Office- US. Cl. 252-62.9 4 Claims ABSTRACT OF THE DISCLOSURE Ferroelectric and piezoelectric composition comprising a solid solution of the ternary system is disclosed. The constituents are defined by the formula X +Y+Z=100,

wherein X, Y and Z are in the following ranges, taken with reference to the figure ABCDEFGH in FIG. 1:

X Y Z BACKGROUND OF THE INVENTION Field of the invention The invention relates to a novel ferroelectric and plezoelectric composition.

DESCRIPTION OF THE PRIOR ART Ferroelectric and piezoelectric materials containing barium titanate, lead titanate zirconate and the like as their principal constituents are used in many diverse applications, such as transducers useful in devices such as wave filters for producing or sensing vibrations, elements for generating high voltage and the like.

SUMMARY OF THE INVENTION The present invention relates to a ferroelectric and piezoelectric material having a novel composition.

A ferroelectric and piezoelectric material prepared in accordance with the present invention is characterized by intense ferroelectric and piezoelectric properties wh ch are obtained by applying a DC voltage to a sintered ceramic material in the same manner by which ceramics of barium titanate or lead titanate zirconate are made, thereby polarizing the ceramic and providing a residual polarization to the ceramic. This property enables the ceramic to be advantageously used in transducers in all types of electrical devices.

BRIEF DESCRIPTION OF THE DRAWINGS -FIG. 1 is a triangular compositional diagram illustrating the various embodiments of the present invention.

FIG. 2 is a diagram illustrating curves Which indicate variations in the longitudinal coupling coefiicient and the dielectric constant, respectively, of the material produced in accordance with the present invention when the ratio of lead titanate with respect to lead indate niobate is varied.

FIG. 3 is a diagram illustrating the curves which indi- 3,630,908 Patented Dec. 28, 1971 cate the variation in the longitudinal coupling coefiicient and the dielectric constant, respectively, of the material produced in accordance with the present invention when the ratio of lead titanate with respect to lead zirconate is varied and the content of lead indate niobate in the material is held to 10 mol percent.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The material produced in accordance with the present invention is composed of Pb(In /2Nb /2)O -PbTiO PbZrO All of the ceramics made of the ternary system in accordance with the present invention possess piezoelectric properties. However, from the view of industrial interest, the subject matter of the present invention is directed to the following range of each constituent of the material referred to in the diagram in FIG. l:

X=5-70 mol percent. Y=2555 mol percent. Z=06O mol percent.

wherein X Y+Z=100z The values of the coupling coefficient k and the dielectric constant e of the material are max mums at positions adjacent to the phase boundaries of is superior from the viewpoint of easiness of sintering and polarization of the material in comparison with the binary system consisting of PbTiO -PbZrO Further, the Curie point of the composition containing Pb(In /2Nb /z)O is higher than that of the composition which does not contain Pb(Irr /2Nb /2)O The Curie point of composition sample number 16 is about 50 C. higher than that of a binary system in which the ratio of Zr to Ti is kept at about the same ratio as that of sample number 16. Accordingly, the lower limit of the composition wherein the inclusion of Pb(In /2Nb /2 )03 is recognized to give advantageous results is represented by the numerals C-D- E-F in FIG. 1.

In preparing the ceramic in accordance with the pres ent invention, oxides such as ln O Nb O TiO ZrO The' oxides in Table 1 were used as raw materials in powdered form since these were commercially available at a purity greater than 99.5%. The oxides were mixed together after each of the oxides was weighed to obtain the weight ratio shown in Table 1. The mixture was then dried, and heated at 800 C. for two hours so as to elfect a temporary sintering thereof.

The temporarily sintered material was coarsely crushed, finely powdered and wet blended in a ball mill for 20 hours.

After the powdering and blending, an organic caking agent was added to the powder, and the thus prepared mixture was pressed so as to form a cylindrical shape having a diameter of 6 mm. and a length of 18 mm. The thus formed body was sintered in a platinum casing at a temperature ranging from 1230 to 1270 C. for three hours within an atmosphere of lead. The sintered body was ground into a shape having a diameter of mm. and a length of mm. with the opposite ends of the body being glazed with silver paint.

The thus formed element was polarized by applying a DC voltage of 2.5 kv./mm. in silicone oil at a temperature of 100 C. After the expiration of 100 hours from the time of polarization of the element, the physical properties of the element were measured by the methods defined by the IRE standard. Table 1 shows the test results, the longitudinal coupling coefficient being indicated by k and the dielectric constant being indicated by e. The variation in properties due to the change in the ratio of Pb(In /2Nb /2)O with respect to PbTiO is shown is FIG. 2. The variation in the properties due to the change in the ratio of PbZrO with respect to PbTiO when the content of Pb(In /2Nb /2)O is kept at 10 mol percent is shown in FIG. 3.

TABLE 1.-COMPOSITIONPROPERTIES (Refer to Figure 1) Composition, mol percent Sinterlng 1:33,

temp, per- Pb(In Nb )O3 Pb'IiOs PbZrOi C. cent e 80 0 1230 22 500 75 25 0 1230 40 810 70 0 1230 52 1, 100 65 0 1250 57 1, 300 60 0 1250 50 1, 020 55 O 1250 40 800 50 0 1250 27 680 45 0 1250 12 580 G0 30 10 1250 42 870 50 30 20 1, 250 41 500 40 30 3O 1, 250 42 550 30 30 40 1, 250 45 420 20 30 50 1, 250 46 530 10 30 1, 270 45 500 50 4O 10 1, 250 53 760 30 40 30 1, 250 61 1, 20 40 40 1, 250 56 630 10 40 50 1, 250 60 320 Sample numbers 26 and 928 are included within the claims, whereas sample numbers 1, 7, 8 and 29-33 are excluded from the claims for the previously mentioned reasons though they also illustrate the piezoelectric properties.

It is well known in the art that mechanical losses in a ceramic composed of the ternary system PbZrO -PbTiO PbSnO can be reduced, and the dielectric constant thereof increased, by replacing a portion of the Pb+ with an alkaline earth. A similar effect can be obtained in the ternay system Pb(ln /2Nb /2 )O -PbTiO -PbZrO produced in accordance with the present invention by replacing a part of the Pb' with an alkaline earth.

What is claimed is:

1. A ferroelectric-piezoelectric composition consisting essentially of a binary system consisting of and PbTiO said Pb(In /2Nb /2)O being present in amounts of from about 55 to about 75 mol percent and said PbTiO being present in amounts from about 45 to about 25 mol percent.

2. A ferroelectric-piezoelectric composition consisting essentially of a solid solution of a ternary system consisting of about 10 mol percent Pb(In/2Nb /2)O from 45 to 50 mol percent of PbZrO and from 40 to 45 mol percent of PbTiO 3. A ferroelectric-piezoelectric composition consisting essentially of a solid solution of a ternary system consisting of about 30 mol percent of Pb(In /2Nb /2)O from 25 to 30 mol percent of PbZrO and from 40 to 45 mol percent of PbTiO 4. A ferroelectric-piezoelectric composition consisting essentially of a solid solution of a ternary system consisting of about 50 mol percent of Pb(In /2Nb /2)O from 5 to 10 percent of PbZrO and from 40 to 45 percent of PbTiO References Cited UNITED STATES PATENTS 9/1969 Kurihara et a1 25262.9

TOBIAS E. LEVOW, Primary Examiner J. COOPER, Assistant Examiner US. Cl. X.R. 10639 R 

